I missed the poll for this one, where I would have recommended the Ergotron 45-241-026 LX Desk Mount. Good for 20 lbs, monitors up to 3" deep. Holds my Monoprice 27" Zero-G reliable,. and hasn't gotten loose in over a year even though I reposition it repeatedly through the business day. I'd like a 2nd one for the home office.

http://www.newegg.com/Product/Product.aspx?Item=N82E16824994063

Speaking of Monoprice, they have several desk mount brackets rated at over 30 lbs.